1. Field of the Invention
Embodiments disclosed herein relate to a rotary electric machine.
2. Description of the Related Art
Japanese Utility Model Publication No. H7-036459 discloses a rotor including a laminated iron core, which has an annular connecting portion surrounding a rotating shaft and a plurality of sector-like magnetic pole portions integrally formed with the connecting portion in a number corresponding to a pole number, and a plurality of rectangular permanent magnets arranged between the magnetic pole portions. Punched holes, each of which has enlarged portions at the opposite ends thereof, are formed over the magnetic pole portions and the connecting portion of the iron core. Non-magnetic reinforcing members are filled and inserted into the punched holes.
Rare earth magnets such as neodymium magnets or the like are extensively used as permanent magnets of a rotor for a rotary electric machine. The rare earth magnets are high in magnetic flux density and, therefore, are capable of reducing the size of permanent magnets of a rotor. However, the rare earth magnets suffer from the disadvantage of high cost. In view of this, it is thinkable to use inexpensive magnets such as ferrite magnets or the like. In this case, however, it is necessary to increase the volume of permanent magnets because the ferrite magnets are lower in magnetic flux density than the rare earth magnets.
The conventional rotor referred to above is provided with the punched holes for preventing magnetic flux leakage between the permanent magnets. This limits the dimensions of the permanent magnets in the radial direction and in the direction perpendicular to the radial direction. It is therefore difficult to increase the volume of the permanent magnets without making the diameter of the rotor larger. On the other hand, if the punched holes are omitted in an effort to increase the volume of the permanent magnets, the leaked magnetic flux grows larger. Thus, there is a problem in that the decrease of the leaked magnetic flux and the increase of the volume of the permanent magnets are not compatible.